1. Field of the Invention
The present invention relates to a method for frequency reuse, and more particularly to a method for fractional frequency reuse with ordering scheme to increase capacity of orthogonal frequency division multiplexing (OFDM) systems.
2. Description of the Related Art
Growth of wireless subscribers and proliferation of multimedia services has increased demand for bandwidth in wireless access. Therefore, next-generation wireless access networks require an advanced technique that has the ability to mitigate frequency selective fading in wideband communications and to utilize the frequency spectrum efficiently. Orthogonal frequency division multiplexing (OFDM) is considered one of the best solutions to satisfy these requirements. In wireless cellular communication systems, cell clustering is often used to reduce the effects of co-channel interference (CCI) from neighboring cells. To increase the efficiency of a system, the frequency reuse factor should be close to 1.
Reduction of CCI, however, is achieved at the cost of reduced cell capacity. To mitigate such tradeoffs, some techniques such as sectoring, reuse partitioning and fractional frequency reuse (FFR) have been studied.
Sectoring uses directional antennas to increase cell capacity, and reuse partitioning uses multiple reuse factors. Overlaid cells are implemented for reuse partitioning to increase the capacity of a system and to reduce the CCI. In FFR, constraints on usable sets of channels balance the tradeoff between cell capacity and interference. Thus, conventional FFR has a problem of restricting the spectrum effect of a system since there are many constraints on sub-channel sets used in every cell.